I also urge anyone, but especially Canadians to visit the Vimy battlefield. The tunnel is not to be missed, and I remember stuff embedded in the walls. I took a couple of pictures, but with a cheap camera, and they aren't as good as that one. I was talking to an ex-Royal Engineer I knew when I lived in England, just before I made the trip, and he told me about clearing the site - as safe as you can think possible, he said, but no guarantees.
(It's a bit of a shame they had to get the British Army to do it, but apparently when the project got to that stage Canadian Forces had all its Engineer assets committed elsewhere. At least that is what he was told. It was easier for the British Army of the Rhine, of course, being much bigger and much closer than our brigade group in the south.)